Automatic followup controller for a turbine

ABSTRACT

An automatic followup controller for a back pressure type or air bleed back pressure type turbine which can be operated under either of control operation and pressure control operation, in which means is provided for adjusting the setting of speed governor means to follow the actual operating condition during a pressure control operation and for adjusting the setting of pressure governor means to follow the actual operational condition during a speed control operation, so that, when the operational condition is switched from the pressure control operation to the speed control operation, or vice versa, no abrupt change in load or speed on the turbine or a generator connected to the turbine and a smooth conversion of operation can be performed, and selector means is provided in each of passages which supply pressurized hydraulic oil from said pressure governor means and said speed governor means and said speed governor means to a servomotor means which controls a turbine control valve, said selector means being operative to selectively direct pressurized hydraulic oil from either one of said governor means to said servomotor means.

United States Patent [72] Inventors Matuto Kikuchi;

Tomoyuki Nakatsuka. both of Hitachi-shi, Japan [2 l] Appl. No. 840,223 {22 Filed July 9. 1969 {45] Patented Aug. 3, 1971 [73] Assignee Hitachi, Ltd.

Tokyo, Japan [32] Priority July 10, 1968 [33] Japan [31} 43/47761/68 [54] AUTOMATIC F OLLOWUP CONTROLLER FOR A TURBINE 7 Claims, 8 Drawing Figs.

[52] U.S.Cl 415/17 [51] lnt.C| F0lb 25/00 [50] Field otSearch 415/17 [56] References Cited UNITED STATES PATENTS 2,977,768 4/1961 Wagner etal 415/17 3,342,195 9/1967 Wagner ABSTRACT: An automatic followup controller for a back pressure type or air bleed back pressure type turbine which can be operated under either of control operation and pressure control operation, in which means is provided for adjusting the setting of speed governor means to follow the actual operating condition during a pressure control operation and for adjusting the setting of pressure governor means to follow the actual operational condition during a speed control operation, so that, when the operational condition is switched from the pressure control operation to the speed control operation, or vice versa, no abrupt change in load or speed on the turbine or a generator connected to the turbine and a smooth conversion of operation can be performed, and selector means is provided in each of passages which supply pressurized hydraulic oil from said pressure governor means and said speed governor means and said speed governor means to a servomotor means which controls a turbine control valve, said selector means being operative to selectively direct pressurized hydraulic oil from either one of said governor means to said servomotor means.

Patented Aug. 3, 1971 3,597,101

4 Sheets-Sheet 1 RPM T L sec INVENTOR$ MAT'LITO KrKu nr and rOM YuKL NAKATSMKA Z AZ WM} q/ ATTORNEYS Patented Aug. 3, 1971 4 SheetsSheet 2 FIG. 3

OUTPUT INVENTORS MATHTO KIKMCHI and T Y NAKATSHKA ATTOR N [5Y5 Patented Aug. 3, 1971 4 Sheets-Sheet 5 FIG. 7

lNvENToRs NA K AT 5 u KA MATuTO KIKMLHII 4nd TOMOYuKL ATTORNEY Patented Aug. 3, 1971 3,597,101

4 Sheets-Sheet 4 FIG. 8 mp INVENTORS MAruTo KLKucHL' and I0/V\OYL(I\"L' NAK 'SHKA ATTORNEYS .-\L'TO.\I.-\TIC FOLLOWL'P CONTROLLER FOR A TURBINE BACKGROUND OI- THE INVENTION The present invention relates to a back pressure type turbine or an air bleed back pressure type turbine (hereinafter simply referred to as a back pressure type turbine). and more particularly to an automatic followupcontroller for enabling in such a type of turbine to convert the operation of a turbine smoothly from a pressure control operation in which a turbine back pressure is governed. to a speed control operation in which the rotational speed of the turbine is governed. or vice versa. without subjecting a turbine generator to a sudden change of load or speed.

In a back pressure type turbine. it is impossible to perform both a speed control which utilizes speed governor means and a tubine exhaust pressure (back pressure) control which utilizes pressure governor means at the same time. If a turbine were so designed that the speed control and the back pressure control were simultaneously performed. the speed governor means and the pressure govemor means would interfere with each other so that a stable turbine control would not be obtained. For this reason, it has been a common practive to operate a turbine with either one of the governor means inoperative. In a back pressure type turbine of this kind. when it is desired to perform a pressure control operation. a turbine generator is connected with another electrical system to maintain he rotational speed of the turbine substantially constant. and the back pressure control is performed by means of the pressure governor means with the speed governor means inoperative. In a conventional arrangement. during a pressure control operation wherein a turbine generator is operated in a parallel relation with an external electric power source. if the generator is disconnected from the external electric power source due to some possible reasons. an automatic switching means operates to make the pressure governor means inoperative and at the same time to cause the speed governor means start into operation. In this instance. it is usual that the opening ofa control valve provided at the entrance of the turbine varies abruptly.

This is due to the fact that. in a conventional turbine control means. the pressure governor means and the speed govemor means are arranged in series in a pressurized hydraulic oil passage which is leading to a servomotor for controlling v the control valve provided at the entrance of the turbine. Since the area of the oil passage in the speed governor means is larger than that of the pressure governor means during the pressure control operation. as soon as the operation is switched from the pressure control operation to the speed control operation. the opening of said control valve abruptly increased so that it corresponds to the area of the oil passage in the speed governor means. Similarly. when the operation is switched from the speed control operation to the pressure control operation. the opening of the control valve is also abruptly changed. The change in rotational speed of the turbine generator. which will thus occur during the switching of operation from the speed control operation to the pressure control operation. will have a great influence on the operations of various machines which are operated with an electric power supply from the generator. Therefore. depending on the type of production. the quality of products manufactured by such machines will possibly be adversely affected. (For example. in a yarn manufacturer. the denier number of yarns would vary. and in a paper manufacturer. the weight or thickness of papers would vary.) Thus. it has been desired to obtain governor means which is elTective to prevent such a change in rotational speed of a turbine during switching of the operation. For this purpose. various types of governor'- means has hithertofore been developed. However. these conventional means have the following disadvantages:

I. When the pressure governor means and the speed govemor means are designed to have oil passages of substantially equal area. both of the means interfere with each other. so

that the ranges of the setting value of the pressure governor means and the speed governor means. to which the operation of the turbine is intended to fOllOVt. are accordingly limited.

2. In a governor means in which the difference between the actual load during the pressure control operation and the setting value of the speed governor means by means of a microswitch in order to operate a governor motor so that the setting value of said speed governor means is adjusted in accordance with the actual load. due to the time required in operation of the governor motor and the inertia thereof. substantial time is required until the setting value is adjusted to an appropriate value after it is detected. If during this period of adjustment. said switching of operation occurs. a sudden change of the opening of the control value cannot be avoided.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the aforementioned disadvantages of the conventional means and to provide an automatic followup control means which can adjust the setting of the speed governor means in accordance with the actual operational condition during the pressure control operation of a turbine or adjust the pressure governor means in accordance with the actual operational condition during the speed control operation. whereby when the operation of the turbine is switched from the speed control operation to the pressure control operation or vice versa. or continued operation of the turbine can be ensured without being subjected to a sudden change of the rotational speed or the load of the turbine.

Another object of the present invention is to provide a control means comprising an automatic switching means for switching the operation of the turbine to either one of the pressure control operation and the speed control operation, said switching means being dual-acting type so that it is effective even when a portion thereof is not working.

A further object of the present invention is to provide a turbine control means having means continuously movable in response to the output of a turbine to indicate the output.

The characterized features of the present invention are in the fact (1) that the speed governor means can be quickly adjusted to a followup setting value directly by hydraulic means but not by means of a governor motor; (2) that a pressure control oil passage and a speed control oil passage are arranged in parallel relation. either one of the oil passages is connected by means of a switching means to a servomotor means for controlling the turbine control. so that both ofthe signal levels for the pressure control and for the speed control can be completely equal; and (3) that said switching means is of a dual acting type so that even when a portion of the switching means is not working it can operate without any inconvenience.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view diagrammatically showing a conventional turbine control means:

FIG. 2 is a diagrammatical view showing the arrangement in a conventional turbine control means:

FIG. 3 is a diagrammatical view showing an embodiment of the automatic followup controller for a turbine embodying the present invention:

FIGS. 4, 5 and 6 show the character of a turbine speed controller:

FIG. 7 is a diagrammatic view of another embodiment of the automatic followup controller for a turbine embodying the present invention: and.

FIG. 8 is a system block diagram showing a further embodiment in which the automatic followup controller of the present invention is applied to both of pressure and speed control systems of a t urbine.

DETAIIED DESCRlPTlON OF THE PREFERRED EMBODIMENTS The outline of a conventional turbine control means will now be explained with reference to the drawings. Referring to FIG. I. the reference numerical I shows pressure governor means. a speed governor means 2. a load limiter 3 and a servomotor means 51: for actuating a control valve 6 which controls the flow of hydraulic fluid supplied to a turbine 61. As shown. the pressure governor means I. the load limiter 2 and the speed governor means 3 are arranged in series in a oil passage leading to the servomotor means 50. Since the oil passage of the speed governor means 3 is larger than that of the pressure governor means 1 during a pressure control operation of the turbine. when the operation of the turbine is switched from the pressure control operation to a speed control operation. the opening of the control valve is suddenly increased so that it corresponds to the oil passage of the speed governor means. Thus. the rotational speed of the turbine is increased to a certain value.

FIG. 2 is a diagrammatical view which shows the aforementioned conventional turbine control system in more detail. In this figure. during the pressure control operation, a pressurized hydraulic oil 11 from a main pump (not shown in the drawing) is controlled by means of a pressure control pilot valve 12 connected to a pressure control mechanism 1. and directed through the load limiter 3 and a speed control pilot valve 21 to a hydraulic piston to allow the turbine to operate with an output corresponding to the amount of turbine exhaust or turbine back pressure. In this instance. the speed control pilot valve 2i and a pilot bushing 22 (refer to numeral 22 in FIG. 7) thereof are so arranged that they do not control the pressurized hydraulic oil. Thus, the speed control mechanism 2 does not control the pressurized oil. FIG. 4 shows the character of the speed governor means of the turbine, in which the abscissa expresses the output of a turbine generator and the ordinate expresses its rotational speed or frequency. In an operational condition in which the speed governor means is inoperative, its setting is determined to a value H which is higher than the rated rotational speed N, as shown by a straight line a in FIG. 4. Supposing that the turbine output is P and the rotational speed is N and that the turbine is operated in a pressure control condition with the turbine generator arranged in a parallel relation with an external electric power source, if said generator is disconnected from the external electric power source and the operation of the turbine is switched to the speed control condition. the control valve is further opened so that the rotational speed of the turbine is increased from N to H. Thus, if the turbine load P remains constant before and after the generator is disconnected from the external power source, the speed governor means will control the turbine so that its rotational speed becomes H.

In case where it is possible that the variations in rotational speed of the turbine have adverse efi'ects on the quality of products manufactured in a factory utilizing the power of the turbine generator, in order to limit the increase of the turbine rotational speed within an acceptable limit of (refer to FIG. 4). it is usual to operate the turbine with the speed governor means serving to a certain amount to limit the oil passage during the pressure control operation so that the setting of the speed governor means is displaced from the line a to a and that the difference Af between the rated rotational speed N of the turbine and the set value H of the speed governor means is always constant. FIG. 2 will now be explained in relation to FIG. 4. Suppose that. when the turbine is operated with a pressure control condition and with an output P. the amount of working fluid exhausted from the turbine is decreased and the output is decreased to P1. In this instance. if the automatic followup controller does not operate to control the setting of the speed governor means. the rotational speed setting of the speed governor means will be H" at the output of P.. so that the difference Af between the setting speed and the rated rotational speed will become larger than that when the output is P. In order to maintain the difference Af substantially constant, the following means have been conventionally employed.

When the output is changed from P to P and the hydraulic piston is lowered in the direction shown by an arrow X, a return lever 23 for the speed governor means is rotated counterclockwise about a movable fulcrum 73 comprising a portion of a synchronizing means 7. whereby a pilot bushing 22 of the pilot valve 21 for the speed governor means is moved downwardly. Thus. the relative position between the pilot bushing 22 and the pilot valve 21 is varied. so that the restriction of the oil passage 22a is slightly opened. By this movement, the setting of the speed governor means is varied from H to H" (refer to FIG. 4). At the same time. the followup lever 24 is rotated counterclockwise about a fulcrum located at an intermediate portion of the lever until a switch actuator 29 carried at the right end of the lever closes a lowering contact 28L of a microswitch 28. Thus, the governor motor 71 is caused to rotate to decrease the turbine rotational speed. Then, the movable fulcrum 73 of the synchronizing means 7 is upwardly displaced as shown by an arrow Y, so that the pilot bushing 22 is upwardly moved through the return lever 23. Simultaneously with the upward movement of the movable fulcrum 73, the microswitch 28 is also moved upwardly, so that the contact of the switch 28 is again opened when the fulcrum 73 is upwardly moved by a predetermined distance and the rotation of the governor motor 71 is stopped. Thus, the movements of all of the parts are stopped. In this manner, the governor motor 71 is caused to rotate by such an amount that corresponds to the increase in the amount of ofiset of of the setting of the speed governor means so that the increase can be automatically compensated to maintain the value Af substantially constant.

The disadvantages of the conventional means have already been set forth, but the important ones will now be described in more detail taking reference to FIG. 2. (I) Since in this known arrangement the pressure governor means 1 and the speed governor means 2 are disposed in series in the oil passage of the pressurized oil 11 leading to'the servomotor means 50, it is impossible to make the restriction of the oil passage in the pressure governor means I and that in the speed governor means 2 due to the mutual interference therebetween. Therefore, the size of the oil passage in the speed governor means 2 should necessarily be greater than that in the pressure governor means 1. For this reason, the value Af shown in FIG. 4 cannot be sufficiently reduced and it is very difficult to satisfy the requirements of users for marking as small as possible the abrupt change of the turbine rotational speed when the operation of the turbine is switched from the pressure control condition to the speed control condition. (2) When the amount of offset Af is automatically compensated, the offset is detected by the switch 28 and the compensation is performed by a governor motor 71. However, the accuracy of detection by the microswitch is generally unstable, and even a small difference in the detecting function has a great influence on the amount of offset, so that an accurate followup control cannot be expected. (3) When the lever mechanism 23 is operated by the rotation of the governor motor 71, the inertia of the governor motor may possibly cause an overadjustment of the value M (4) Since a substantial time is consumed until the setting of the speed governor means 2 is readjusted by the governor motor 71 from the instant when the variation in turbine load is detected by the switch 28, if the operation of the turbine is switched from the pressure control condition to the speed control condition during this transient period, the rotational speed of the turbine will be abruptly changed.

The present invention provides an automatic followup means in which the above-mentioned disadvantages are eliminated. P16. 3 is a diagrammatical view showing one embodiment of an automatic followup controller for a turbine embodying the present invention. In this arrangement, a speed control pilot valve 21 is disposed above a speed control mechanism 2a, and a pilot valve bushing 22 which cooperates v with the pilot valve to control the hydraulic pressure for controlling the speed is connected with a lever 23. The lever 23 is connected at one end with a rod 52 and at the other end with another rod 75. both of the rods 52 and 75 are respectively connected with a return lever 74 of a synchronizing means. Above the speed control pilot valve 21. there is provided a followup pilot valve 81 which is integrally manufactured with the pilot valve 21. and a followup pilot valve bushing 82 which cooperates with the pilot valve 81 for producing a followup control hydraulic oil pressure is connected with the return lever 74. The rod 52 has a lever 51 rotatably connected thereto at 5211. The lever 51 has one end connected with a stem 5b of a hydraulic piston 5 in a servomotor 50 for actuating a control valve 6. and the other end connected with the lower end of a stem 83a of a followup piston 83.

A pair of microswitches are disposed above the followup piston means 8 and adapted to be actuated in response to ther vertical movement of the followup piston 83 to cause the governor motor 71 to rotate or stop.

Automatic switching means 4 is employed for leading a pressurized hydraulic fluid either from the speed control pilot valve 21 and the pressure control pilot valve 12 through the load limiter 3 into the hydraulic piston 5. and diagrammatically shown in FIG. 3 in the form of a three-way valve. However. its actual construction is dual-actuating longitudinally slidable pilot valve type as shown in FIG. 7 and the detail thereof will be described later. Further, in FIG. 3, the connections between the levers and the rods identified by thick dots are rotatable connections.

In FIG. 3. the parts are shown in positions in which the turbine is under a pressure control operation and the speed to both of the levers 23 and 74. so that the levers 51, 23 and 74 and the rods 52 and 75 constitute a followup assembly. The aforementioned downward movement of the lever 51 causes said assembly to move downwardly about a movable fulcrum 73 of the synchronizing means 7. and thus the levers 74 and 23 are displaced to positions shown by dotted lines 74a and 230 respectively.

When the lever 23 is displaced to the position shown as 23a, the speed control pilot valve bushing 22 which is connected thereto is also caused to move downwardly, whereby the bushing is downwardly, displaced from the neutral position with respect to the speed control pilot valve 21. Thus, a

governor means is performing the automatic followup control. The pressurized hydraulic oil HP from a main hydraulic pump (not shown) is adjusted to a predetermined pressure by the pressure control pilot valve 12 which is connected to the pressure control mechanism In responsive to the turbine back pressure. and directed through the automatic switching means 4 and the load limiter 3 into the hydraulic piston 5 of the servomotor 5a to control the opening ofthe controlyalve 6 U On the other hand, the pressurized hydraulic oil 11S is directed, through the speed control pilot valve 21 which is connected to the speed control mechanism 20 responsive to the speed of the turbine. into a speed control pressure pipe 26 where it is blocked by the automatic switching means 4. Thus. the oil 118 does not act on the piston 5 and the turbine is operated under a pressure control condition. In this condition. as the back pressure of the turbine increases, the

displacement of the pressure control mechanism 10 increases and the amount of opening at the oil port 12a of the pressure control pilot valve 12 decreases resulting in an decrease of the hydraulic pressure for pressure control. Due to this decrease in the hydraulic pressure for pressure control, the hydraulic piston 5 is moved downwardly whereby the amount of opening of the control valve 6 is decreased and thus the turbine output is reduced.

In this conditiori as prilrdiigiy pointed out. if the speed governor means has no followup function. the relative movement between the speed control pilot valve 21 and the pilot bushing 22 thereof will be such that the setting of the speed governor means is in effect increased.

According to one embodiment of the present invention shown in FIG. 3. even when the hydraulic piston 5 is downwardly moved, the relative positions of the speed control pilot valve 21 and the pilot bushing 22 are not varied and kept in a neutral position. Thus. the turbine can always be controlled at the actual rotational speed. As the hydraulic piston 5 is downwardly moved. the lever 51 is rotated counterclockwise about its right end and momentarily displaced to a position shown by a dotted line 51a.

The-lever 51 has a rod 52 pivotally connected at 520. and the rod 52 in turn has a pair of levers 23 and 74 connected at the opposite ends thereof. A rod 75 is further connected condition which is equivalent to an increased speed governor setting can momentarily be produced. On the other hand. when the lever 74 is downwardly displaced to the position shown at 74a. the bushing 82 for the followup control pilot valve 81. which is connected thereto, is also caused to move downwardly, with the result that the neutral relationship between the bushing 82 and the followup pilot valve 81 is momentarily broken. Thus, the hydraulic oil pressure HT is directed through an upper oil port 82b of the bushing 82 and a passage 85 into the lower side of the followup piston 83to c ause the piston to move upwardly.

By this upward movement of the followup piston 83, the lever 51 is displaced from the position 51a to the position 51b. At the same time, the lever 74 is returned from the position 74a to the initial position shown by a solid line. The lever 23 is also returned from the position 23a to the initial position. When the lever 74 is returned to the initial position, the pilot valve 81 and its bushing 82 are returned to their neutral relationship.

Although the speed control pilot valve bushing 22 and the followup pilot valve bushing 82 are separately made with each other, the lengths of the rods 75 and 52 which are connected to the levers 74 and 23 are so determined that the oil port control spool portions of the speed control pilot valve 21 and the followup control pilot valve 81 and the oil ports in the bushings 22 and 82 exactly correspond with each other, so that the bushings 22 and 82 can operate as a unit. Therefore, when the followup control pilot valve 81 and its bushing 82 are in the neutral relationship, the speed control pilot valve 21 and its bushing 22 are also in the neutral relationship.

As described above, even when the hydraulic piston 5 for actuating the control valve is upwardly or downwardly moved in response to the amount of turbine exhaust, the setting of the speed governor means is not changed. Therefore, even when the turbine operation is switched from the pressure control operation to the speed control operation, the speed governor means can maintain the speed of that moment and continuously control the turbine taking the place of the pressure governor means.

The above described feature will now be described with reference to F IG. 5 in connection with operational characteristics. When the turbine is operated under a pressure control condition with an output P. the speed governor means is set along the line a with the amount of offset Af is equal to zero. In this condition, when the turbine output is decreased to P the setting of the speed governor means is varied from the line a to the line a so that the amount of offset Af is maintained to be zero. Thus, the setting of the speed governor means is automatically adjusted in response to variation in turbine output.

It should be noted that the adjustment of the setting of the speed governor means is obtained not by any manual acutation of the synchronizing means 7 shown in FIG. 3 or the governor motor 71, but by followup piston means responsive to the followup control pilot valve through the aforementioned simple followup assembly.

In a conventional control means, the setting position of the synchronizing means 7 is indicated. In the control means according to the present invention, in order to indicate the turbine output in the term of the setting of the synchronizing means 7, the microswitches 861-1 and 8 6L are connected to the governor motor 71. Thus. when the followup piston 83 is displaced from the predetermined neutral position. the fact is detected by either one of the switches 86H and 86L. whereby the governor motor 71 is caused to rotate so as to actuate the synchronizing means until it is adjusted to a position corresponding to the turbine output.

The present invention will now be described in connection with a particular situation in which the turbine output is decreased. As the output decreases. the hydraulic piston is downwardly moved and. as described previously. the followup piston 83 is upwardly moved. Thus. the switch actuator 87 causes the contacts of the switch 86L so as to rotate the governor motor 71 in the direction in which the speed setting of the speed governor means is decreased. whereupon. the movable fulcrum 73 provided in the synchronizing means 7 is upwardly moved. so that the setting of the synchronizing means 7 is indicated by a suitable means such as a needle secured to the fulcrum. and at the same time, the lever 74 is upwardly moved to the position shown by 74b.

Thus, the bushing 82 for the followup control pilot valve is shifted upwardly and the neutral relationship between the bushing 82 and the pilot valve 81 is broken, whereupon the pressurized hydraulic oil HT is directed through a lower port 820 of the bushing 82 and the oil passage 84 into the upper side of the followup control piston 83 so as to exert a downward pressure on the piston.

As the result. the lever 51 is returned from the position 51b to 51a. and the lever 74 is moved from the position 74b to the position 740. Simultaneously. the lever 23 is moved to the position 23c. Thus. all of the return movements are completed. The followup adjustment of the setting of the synchronizing means is aimed only to establish the relation between the turbine output and the indication of the setting of the synchronizing means. Therefore. its followup rate and the accuracy of the followup function does not effect on the accuracy of the pressure governor means and the speed governor means.

According to the present invention, it is possible to add to the speed governor means an advantageous function which could not be obtained by a conventional means. The setting of the movable fulcrum 73 of the synchronizing means 7 is determined to move along the line a.,. i.e. to a position in which the rated rotational speed is obtained when the turbine load is nought. and the connection between the switches 86L and 86H and the governor motor 71 is disconnected by a switch 88, whereupon the speed governor means is allowed to automatically follow the operational condition when the turbine is operated under the pressure control condition. In this condition. if the turbine load is completely shut down. the automatic switching means 4 operates so that the control of the turbine is performed by the speed governor means. Since the movable fulcrum 73 of the synchronizing means 7 is located to a position corresponding to the noload rated rotational speed. the position of the pilot bushing 22 for the speed control pilot valve 21 is also located in such a position corresponding to the rated speed of the turbine when the load of the turbine is zero. On the other hand. the supply of the pressurized hydraulic oil llT to the followup control pilot valve 82 and the followup piston means 8 is interrupted when the turbine is operated under the speed control condition. so that the followup piston means 8 and the followup control pilot valve 82 becomes inoperative.

Therefore. as described above. when the turbine is operated with full load under the pressure control operation. and the speed governor means is allowed to automatically follow with the switch 88 off. if the whole load is suddenly removed. the turbine speed varies as shown by a curve I; in FIG. 6 and always gets the rated speed.

In FIG. 6, the curve a represents the speed variation in a conventional turbine using a conventional speed governor means observed when the load on the turbine is shut down.

FIG. 7 is a diagrammatic view showing the arrangement of FIG. 3 in more detail. In this figure, a lock means 9 which cannot be seen in FIG. 3 is shown, and the automatic switching means 4 shown in FIG. 3 simply as a three-way valve is shown in greater detail.

The automatic switching means comprises a portion 4A for connecting either one of the pressure control hydraulic fluid or the speed control hydraulic fluid selectively to the servomotor 5a in accordance with the operational condition, and another portion 4B for detecting the disconnection of the turbine generator from the electric system and generating a power signal for switching into the speed control operation.

The portion 4A of the automatic switching means includes a switching bushing 41 which is downwardly biased by means of a spring 415 and upwardly moved by a hydraulic pressure. Within the switching bushing 41, there is disposed a speed governor switching pilot valve 42 which is upwardly biased by means of a spring 44 and downwardly moved by a hydraulic pressure.

The pressurized hydraulic oil 11 from the main hydraulic pump (not shown) is directed through a solenoid valve 48A and a switching valve 47 into a bushing actuating hydraulic cylinder 41 in the portion 4A to cause the bushing 41 to move upwardly to its uppermost position. At the same time. the oil 11 is introduced into the pilot valve actuating cylinder 42P to cause the pilot valve 42 to move downwardly to its lowermost position.

The pressure control hydraulic oil 13 is directed through oil ports 43c, 41!) and 43b. then through a conduit 32 and the load limiter 3 into the servomotor 5a to effect the pressure control operation.

The hydraulic pressure in the bushing actuating hydraulic cylinder 41? in the portion 4A is introduced into the followup control pilot valve 81 and served as a pressure course for the followup control.

The solenoid valves 48A and 48B are employed for actuating the switching means in response to a signal representing a condition that the generator is disconnected from the electrical system. The solenoid valve 48A is normally open and is disengaged when the turbine is operated under the pressure control condition. while the solenoid valve 483 is normally closed and is disengaged during pressure control operation.

Further. the solenoid valve 48A is of such a type that once it is energized to close the oil passage and thereafter the solenoid energizing circuit is opened by a switch (not shown). it is maintained in the closed position so that it is not automatically opened. The solenoid valve 48A is again opened by a manual actuation.

In the arrangemenflas described above. when a switching signal is generated during the pressure control operation for switching into the speed control operation. the solenoid valve 488 is energized to be opened so that the switching valve 47 is upwardly moved through the mechanism which is connected to the solenoid valve. whereby the presurized hydraulic oil which has been supplied to the portion 4A and the followup piston means 83 is exhausted to a drain pipe 478. Thus. the bushing 41 is downwardly moved under the influence of the spring 41S and the speed control hydraulic pressure in the Conduit Zti passes through the oil ports 43a, 41a, 41b and 436, and then through the conduit 32 and the load limiter 3 into the hydraulic cylinder in so as to effect the speed ior trol operation.

At the a'm time. since the hydraulic fluid which has been supplied to the followup pistor rneans 83 and the loclt means 9 is exhausted as described above. the locking piston 92 is downwardly moved under the influence of a spring which is disposed above the piston so as to close the oil passages from the followup control pilot valve 81 to the followup piston 83. whereby the followup function is cancelled.

condition. the supply of the control hydraulic pressure is blocked and the locking means is put into operation so that the followup function can be completely ceased.

The arrangement in which the bushing 41 and pilot valve -32 of the portion 4A are both movable has a special meaning.

If it is only required to selectively introduce the pressure control hydraulic pressure in the conduit 13 and the speed control hydraulic pressure in the conduit 26 into the servomotor A. it would be only necessary to make only one of the pilot valve 42 and the bushing 41 to be movable and the other may be fixed (actually. a hydraulic selector of a conventional construction is designed in such a way). However. if the switching valve cannot perform a required function completely due to some possible reasons. the speed control hydraulic pressure in the conduit 26 cannot be introduced into the servomotor 50. so that. even if the setting of the speed governor means is perfectly adjusted. the speed control will become impossible after the turbine generator is disconnected from the system electric source resulting in a possible accident.

In order to eliminate the possible dangerous situation, according to the present invention. the switching bushing 41 and the pilot valve 42 are both movable. and in addition to that. they are moved in the directions opposite to each other. F urthermore, the hydraulic pressure from the switching valve is directed to act on both of the bushing 41 and the pilot valve 42. so that upon completion of their operation, the switching from the pressure control operation to the speed control operation can be perfectly achieved. In order that the dual acting switching means is operated. it is necessary that the solenoid valve 488 is energized to actuate the switching valve 47 through the mechansism 100 so that the hydraulic fluid in the conduit 46 is exhausted. however. there is no assurance that the switching valve 47 is always perfectly actuated and there is a possiblity of incomplete operation.

In order to compensate for this incompleteness. there is provided a solenoid valve 48A. The hydraulic pressure from the main hydraulic pump is normally introduced through the solenoid valve 48A into the cylinder of the portion 48. When a signal for switching into the speed control operation is received. the supply of the hydraulic pressure 11 into the portion 48 is stopped and the pressure from the switching valve 47 is exhausted. Thus. upon receipt of the signal for switching into the speed control operation. the hydraulic fluid in the conduit 46 is exhausted through both of the solenoid valve 48A and the switching valve 47.

The present invention has heretofore been described in connection with the construction and the function for automatically adjusting the setting of the speed governor means during the pressure control operation. If it is possible to automatically adjust the setting of the pressure governor means in accordance with the operating condition of the turbine during the speed control operation. the operation of a back pressure type turbine would become more convenient.

When a turbine is started. it is increased in speed up to the rated rotational speed and thereafter connected into an electrical system so that an initial load is applied thereon. Then the operation of the turbine is switched into the pressure control condition and if an emergency condition is encountered during the pressure control operation. it is again switched into the speed control operation. Throughout the whole operation. the pressure governor means automatically follows the actual turbine condition during the speed control operation. while the speed governor means automatically follows the actual turbine condition dun'ng the pressu re control operation. According to this arrangement. the turbine operation can be switched at any time from one of the pressure and the speed control operations to the other without creating any abrupt change in rotational speed of the turbine. so that the switching of the operation can be performed in a stable manner.

I An embodiment of the present invention which can satisfactorily achieve the above function is shown in FIG. 8. In FIG. 8. parts which correspond to those arrangements shown in FIG. 3 are identified by the same reference numerals and the principle therof is substantially identical to the previously described arrangement for performing the automatic followup operation of the speed governor means. so that the construction and the function of this embodiment will be understood from the previous descriptions. Therefore. this embodiment will not be described in detail but will be briefly explained.

In FIG. 8. the turbine is shown in speed control condition. The pressurized hydraulic oil 118 from the main hydraulic pump is supplied through an oil passage constituted by a speed control pilot valve 21S controlled by means of a speed control mechanism 20 and a pilot bushing 22S thereof. and then through a switching means 4 and a load limiter 3 into a servomotor means 50 for actuating a control valve 6.

During the speed control operation, a pressure control followup assembly comprising levers SIP, 23F and 74? and rods 52] and 75P. pressure control followup pilot valve 81? and pressure control followup piston means 8P are in operation, whereby the setting of the pressure governor means is continuously adjusted so that it corresponds to the rotational speed or the load condition of the turbine during the speed control operation. In this instance, the speed control followup assembly comprising levers 515, 238 and 74S and rods 52S and 758 does not perform a followup function.

On the other hand, during the pressure control operation, the speed control followup assembly, the speed control followup pilot valve 818 and the speed governor piston means 88 are in operation. whereby the setting of the speed governor means is continuously adjusted so that it corresponds to the rotational speed and the load conditions of the turbine during the pressure control operation. In this instance, the pressure control followup assembly does not perform a followup operation.

When it is desired, during the speed control operation, to adjust the setting of the speed governor means to a valve which does not correspond to Af =0 but slightly higher than that corresponding to the actual operational condition, the lengths of the rods 52 and 75 may be adjusted with respect to each other. For this purpose, an adjusting portion 76 is provided at the connection between the lever 74 and the rod 52.

The operation of the automatic selecting means for switching the turbine operation from the pressure control condition to the speed control condition was already explained with respect to the embodiment shown in FIG. 7. Therefore, the supply of the pressurized hydraulic oil into the pressure control followup assembly in this operational condition will now be supplementarily explained.

When a signal is generated indicating that the turbine generator is disconnected from the electric power system, the electric solenoid valve 48A is closed and the electric solenoid valve 48B is opened, so that the hydraulic pressure in the conduit 46 is exhausted as previously described.

i-Cs treatments s eadebrinarrr aaarc ressure iiis supplied through the speed governor means 2, the switching means 4A and the conduit 32 into the servomotor means 5a, whereby the turbine operation is switched into the speed control condition. At the same time, the pressurized hydraulic oil which has passed through the solenoid valve 488 is supplied through the conduit 46a into the pressure control lock piston 92? and the pressure control followup pilot valve 82F. Thus. the pressure control followup assembly comprising the levers S ll. 23F and 74F and the rods 52? and 7SP is put into operation.

The present invention has heretofore been described in connection with a back pressure type turbine with respect to the switching between the pressure control operation and the speed control operation, however, it should be noted that the invention is not limited to the application to the back pressure type turbine but is similarly applicable to an air bleed back pressure type turbine, and it is, of course, possible to make various variations and applications without departing the spirit of the present invention.

As apparent from the above description. the present invention provides. in the back pressure type or air bleed back pressure type turbine. means for adjusting the setting of speed governor means so that it always corresponds to the actual operational condition through a followup assembly which is actuated by a hydraulic mechanism when the turbine is operated under the control of pressure governor means. whereby when the turbine generator is disconnected from an electric power system. the turbine operation can be switched into the speed control condition without causing any variation on the rotational speed and the load of the turbine generator.

provided for adjusting the setting of the pressure governor means through a followup assembly which is actuated by a hydraulic mechanism, so that it always corresponds to the actual operational condition of the turbine when the turbine is operated under the control of the speed governor means, whereby when the turbine generator is put into a parallel operation with the electric power system, the operation of the turbine can be switched into the pressure control condition without causing any variation of the rotational speed and the load of the turbine generator.

Still further, according to the present invention, the speed governor means and the pressure governor means have separate setting value automatic followup control mechanisms which are operated hydraulically, and when the turbine is operated under the control of either one of the speed governor means and the pressure governor means (hereinafter referred to as governor means for representing both of the means). the other of the governor means is automatically adjusted so that its setting value corresponds to the actual operational condition, whereby the control of the turbine can be switched from either one of the governor means to the other without creating any abrupt change of the rotational speed and the load of the turbine generator.

Further, according to the present invention, there is provided a followup control means which can actuate synchronizing means through followup piston means which cooperate with said followup assembly and a microswitch, a movable fulcrum of said synchronizing means being displaced in accordance with the output of the turbine. so that the output can be indicated.

Still further, according to the present invention, there is provided a control means having automatic switching means for switching either one of the pressure control operation or the speed control operation of the turbine, said switching means being of a dual-acting type and even when a portion of the switching means is malfunctioning, the switching operation is not interrupted.

We claim:

1. An automatic followup controller for a turbine comprising speed control pilot valve means and pressure control pilot valve means, each of said means being provided one for one servomotor means for actuating valve means to control working fluid into the turbine. said pressure control pilot valve means being connected to a pressure control mechanism for operation in response to the back pressure of the turbine, said speed control pilot valve means being connected to a speed control mechanism for operation in response to the rotational speed of the turbine, and switching means provided in a passage leading from each of the pilot valve means to said servomotor means for selectively directing a pressurized hydraulic oil only from either one of the pilot valve means to said servomotor means. the improvement comprising the provision of followup control pilot valve means integral with said speed control pilot valve means, whereby through followup piston means responsive to said followup control pilot valve means. a setting of pilot bushing means for said speed control pilot valve means is maintained at a neutral position with respect to said speed control pilot valve means during a pressure control operation of the turbine with the intervention of a followup assembly means.

2. An automatic followup controller for a turbine comprising speed control pilot valve means and pressure control pilot valve means, each of said means being provided one for one servomotor means for actuating valve means to control working fluid into the turbine. said pressure control pilot valve means being connected to a pressure control mechanism for operation in response to the back pressure of the turbine, said speed control pilot valve means being connected to a speed control mechanism for operation in response to the rotational speed of the turbine. and switching means pro vided in a passage leading from each of the pilot valve means to said servomotor means for selectively directing a pressurized hydraulic oil only from either one of the pilot valve means to said servomotor means, the improvement comprising the provision of followup control pilot valve means integral with said pressure control pilot valve means. whereby through followup piston means responsive to said followup control pilot valve means. a setting position of pilot bushing means for said pressure control pilot valve means is maintained at a neutral position with respect to said pressure control pilot valve means during a speed control operation of the turbine with the intervention of a followup assembly means.

3. An automatic followup controller according to claim 1, wherein the movement of said followup piston means is detected by switch means, a signal thus obtained being transmitted to synchronizing means so that the position of a movable fulcrum of said synchronizing means is determined according to the output of the turbine.

4. An automatic followup controller according to claim 2, wherein the movement of said followup piston is detected by switch means, a signal thus obtained being transmitted to synchronizing means so that the position of a movable fulcrum of said synchronizing means is determined according to the output of a prime mover.

5. An automatic followup controller according to claim 1, wherein switching means which is provided in each of the passages for directing the pressurized hydraulic oil from said pressure control pilot valve means and that from said speed control pilot valve means to said servomotor means comprises speed control switching pilot valve means and switching bushing means which are slidable in opposite directions with each other under the action of hydraulic pressure and spring means, a pressurized hydraulic oil from main oil pump means being directed, through electrical solenoid valve means responsive to a system disengagement signal, to hydraulic cylinder means for said speed control switching pilot valve means and that for said switching bushing means.

6. An automatic followup controller according to claim 2. wherein switching means which is provided in each of the passages for directing the pressu.ized hydraulic oil from said pressure control pilot valve means and that from said speed control pilot valve means to said servomotor means comprises pressure control switching pilot valve means and switching bushing means which are slidable in opposite directions with each other under the action of hydraulic pressure and spring means. a pressurized hydraulic oil from main oil pump means being directed. through electrical solenoid valve means responsive to a system engagement signal. to hydraulic cylinder means for said pressure control switching pilot valve means and that for said switching bushing means.

7. An automatic followup controller for a turbine comprising speed control pilot valve means and pressure control pilot valve means. each of said means being provided one for one servomotor means for actuating valve means to control working fluid into the turbine. said pressure control pilot valve means being connected to apressure control fiiechanis fn for operation in response to the back pressure of the turbine, said speed control pilot valve means being connected to a speed control mechanism for operation in response to the rotational speed of the turbine. and switching means provided in a passage leading from each ofthe pilot valve means to said servomotor means for selectively directing a pressurized hydraulic oil only from either one of the pilot valve means to said servomotor means. the improvement comprising the provision of speed control followup pilot valve means integral with said speed control pilot valve means. whereby through speed control followup piston means responsive to said speed control followup pilot valve means. a setting position of pilot bushing means for said speed control pilot valve means is maintained at a neutral position with respect to said speed control pilot valve means during a pressure control operation of the turbine with the intervention of a Patent No. 101 Dated August 3, 1971 Inventofls) Matuto Kikuchi and Tomoyuki Nakatsuka It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 11, which now reads:

should read as follows:

Signed and sealed this lhth day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOI'TSCHALK Attesting Officer Commissionerof Patents powso (L591 USCOMM-DC suave-ps9 U S, GUVERNMENT PRINTING OFFICE 1 I959 C|3$-33 

4. An auomatic followup controller ccding o claim 2, heein the movement f said followup piston is detected by switch means, a signal thus obtaine eig transmitte o sycronizig means so hatthe position of movable fulcum f said syncroniig means is determied accordi to the output of a prime move
 5. An utomtic followup controller according o claim 1, herein swichig means hic is provide in each f the passages f diecting he pressuried hyaulic il from said pressure control piot valve means and that from said speed control piot valve means o said servomotor means cmpises speed control swichig piot valve means and switching usig means whichre sliable i opposite directions with each the ude he action f hyrauic pressure and spring means, a pressurie yrauicoi FM mi il pump means being irected, hrouelectrical solenoi valve means responsie o a system isengageme signal to hydraulic cylinder means for si speed control switching pit alvemeans d hat for said swiching bushig means
 6. Anauomtic followup controller according o claim 2, wherein sitchig means hicis provide in each f the passges for irecting he pressurized ydrauic il from said pressure control pilot valve means and that from said speed control pilot valve means to said sevomotor means comprises pressure control switching pilot valve means and switching bushig mes which e sliable in opposite iections with eachothe ude the acting of hydraulic pessure and spring means, a pressurie ydrauic i from mai oi pump means being diecte, hrouhelectrical soleoi valve means responsie o a system engagemet signal to hyrauliccylinder means for said pressure control swichig poilot valve means and hat for said switching ushig means. p,28
 7. n auomatic followup controlle for a turbine comprising speed control pilot valve means and pressure control pilot valve mes, each f said means eingprovied nr for ne servomotor means for actuatig valve means to control working fluid into he tubie, said pressure control piot valve means being connected to a pressure control mechanism for operation in espnse to the back pressure f he uine , said speed control pilot valve means being connected o speed control mechanism for operation in response to he otatinal speed f he ubIe,nd siching means provide in passage edig from each f the pilot valve means to said servomor means for selectively irecting a pessurie hydraulic oil onlyfromeithe ne of hepiot valve means to said servomotor means, he improvemet comprising the provision f spee control followup piot valve means intefral ih said speed control pilot valve means hereby hroughspeed control followup piston means responsive o said speed control followup pilot valve means, setting posiin f piot bushig means for said speed control pit valve means is maitaine t a neutral position with respect o said speed control pilot valve means during pressure control operation f the turbie with he interventin of a speed control followup ssemblymes, nd pressure control followup pilot valve mes intel with said pressure control piot valve means, heeby hrouh pressure control followup piston means responsive o said pressure control followup pilot valve means, a setti position f pilot ushig means fr said pressure control piot valve mes is maintaiedat neural positi wihrespec to said pressure control pilot valve means during spee control operation of the tubine with he ierventi of pressure control followup assembly mes. 